1. Field of Invention
The present invention relates generally to surgical instruments and in particular to instruments for surgery of the eye.
More particularly, the present invention relates to medical instruments used for lamellar keratotomy, known as microkeratomes.
Specifically, the present invention is an improvement to existing microkeratomes in that the invention is disposable thereby replacing the permanent cutting head portion of the existing instruments and increasing the efficience of the microkeratome by increasing the efficiency of operations through the elimination of timely de-contamination procedures on current microkeratomes.
2. Description of the Prior Art
In the field of eye surgery generally, and in the field of keratectomy specifically, a number of devices called microkeratomes have been developed. The microkeratome surgical instrument is used to perform lamellar keratotomy. During the lamellar keratotomy operation, the instrument produces a thin section of the cornea, on which further surgery may be performed. In order to produce the thin section, the instrument must be moved across the ocular globe or eye. The microkeratome excursion may be linear or rotational across the ocular globe. In order to move the instrument a number of means have been utilized including manual, a track and gears or through use of a keyed pivot sweeping the instrument through an arc.
Microkeratomes are comprised of numerous delicate and precision parts. In general, these medical instruments typically differ in their configuration, although having a number of common features. The common features include a vacuum ring to securely grip the ocular globe, a cutting head that includes a plaque and knife edged blade to compress and cut the ocular globe, and a motor/gearing combination that both oscillates the blade and moves the instrument over a given path with respect to the ocular globe.
One configuration in the prior art discloses a microkeratome assembled such that the motor and gearing are directly connected and combined in a common housing or a permanently attached individual housing. The motor and gearing unit is then permanently attached to a cutting head which accommodates the blade. Another configuration disclosed in the prior art utilizes the common features of a motor/gearing combination but accommodates the components in separable housings. Separate accommodations for the motor and gearing requires the combination of the gearing and blade in the cutting head. Each of the configurations described have their individual disadvantages and some common problems.
The configuration uniting the gearing with the motor in a single housing with a permanent attachment to the cutting head also includes a cutting head designed to allow access and removal of the blades. Although the cutting head can be opened to replace the blades, the surface through which the blade protrudes for providing cutting is hinged but does not detach from the cutting head. Since the instrument is ostensibly a single unit with motor, gearing, and cutting head, after each use the entire instrument must endure a sterilization process. Due to the delicate and intricate nature of the instrument, sterilization can be deleterious to the precision gearing and electronics. Therefore the importance of the elimination or reduction in the number of sterilizations is apparent.
Separation of the gearing and motor does not completely solve the instrument sterilization problem. Combining the gearing and cutting head into a removable unit obviates the need to process the motor and electronics with the well known methods of sterilization; however, the complexity and size of the cutting head is increased. In addition, the amount of space available around the ocular globe is limited and restricted by the patient""s anatomy. Thus, while the life of the motor and electronics may be extended, some patients may not be able to accommodate the size of the instrument. Also, unless the entire cutting head assembly is discarded after use, which may be cost prohibitive, the delicate precision gearing is exposed to the sterilization process after each use.
Another consideration fundamental to this type of surgery is the integrity or quality of the cut. Discontinuities or aberrations in the shape of the cut can have serious ramifications on the post-operative vision of the patient. Prior art discloses microkeratomes with characteristics negatively affecting the quality or integrity of the cut. Some of the negative characteristics are poor material properties and compliance, or lack of rigidity of the assembled instrument. The construction of microkeratome components from such materials with unacceptable properties can result in degraded performance for a variety of reasons including dimensional instability. Dimensional instability, such as warping of the cutting head, allows the blade to move in an unplanned manner, which results in an unintended cut shape. Excessive compliance of the assembled microkeratome may result in unintended excursion from the desired path over the ocular globe. Consequently with diminished control of the cutting instrument the quality of the cut is compromised.
In response to the shortcomings described herein, it is a feature of the present invention to provide an improvement to existing microkeratomes wherein the disposable blade housing is independent of the motor, gearing, and cutting head of the microkeratome.
It is another feature that the disposable blade housing improves existing microkeratomes by remaining dimensionally stable, damping vibration and resisting deflection while maintaining the quality of the cut.
It is a further feature that the disposable blade housing improves on existing microkeratome requirements of pre-operative assembly of the instrument.
It is a still further feature that the disposable blade housing improves on the existing microkeratome requirements for sterilization and contamination potential of the surgery.
It is a further feature that the disposable blade housing improves existing microkeratome requirements by providing the disposable blade housing in a limited number of components, such that the overall number of parts are eliminated.
It is a further feature of the invention that the disposable blade housing is composed of materials to reduce the cost of the overall procedure.
The present invention is drawn to a disposable microkeratome for attachment to a guide ring secured to an ocular globe to perform lamellar keratotomy. The microkeratome has a blade assembly with a cutting edge. A cutting head is adapted to join to the guide ring and move in a plane substantially parallel to a surface of the guide ring. The cutting head has an integral compression surface for compressing the ocular globe and a blade slot adjacent the compression surface. The cutting head closely receives the blade assembly such that the cutting edge protrudes through the blade slot toward the compression surface and the blade assembly is restrained to move substantially only along one axis. A motor is releasably attached to the cutting head to osciallate the blade assembly along the one axis.
The cutting head has a lower portion releasably joined to an upper portion and the blade assembly is held between the upper portion and the lower portion. The upper portion has a longitudinal key and the lower portion has a longitudinal keyway adapted to receive the longitudinal key of the upper portion to hold the upper portion and lower portions together. The upper portion has a protrusion and the lower portion has an opening adapted to receive the protrusion and laterally restrain the lower portion with respect to the upper portion. The lower portion is made from a material that is more flexible than the material of the upper portion. The lower portion is a material selected from the group consisting of polymeric, composite, and ceramic materials. The cutting head has an overall height dimension and a height of the lower portion is less than one third the overall height dimension. The lower portion is located within two lower portion height dimensions of a point at which the lower portion joins the guide ring. The motor rotates a pin about a central axis and a blade assembly has a slot that receives the pin.
The invention also encompasses a method of performing lamellar keratotomy on an ocular globe including providing a microkeratome having an upper portion, a lower portion, and a blade. A guide ring is secured to the ocular globe and the microkeratome is joined to the guide ring. The microkeratome is moved across the guide ring to contact the blade with and cut the ocular globe. The microkeratome is removed from the guide ring and the lower portion and blade are disposed of Then, a fresh unused lower portion and blade are joined to the upper portion.